The present invention is directed to air ion generators and, more specifically, to an apparatus and method for improving uniformity and charge decay time performance of an air ionizer blower by redirecting discharged air flow patterns being discharged therefrom.
In many manufacturing and processing environments, it is desirable to prevent the accumulation of charge within a workspace. To prevent the accumulation of charge both positive and negative ions are guided into the workspace to neutralize any charge which may be building up. One example of an industry in which the accumulation of charge in production areas must be avoided is the disk drive industry where it is critical to maintain high manufacturing yields.
Air ionization is an effective method of eliminating static charges on non-conductive materials and isolated conductors. Air ionizers generate large quantities of positive and negative ions in the surrounding atmosphere which serve as mobile carriers of charge in the air. As ions flow through the air, they are attracted to oppositely charged particles and surfaces. Neutralization of electrostatically charged surfaces can be rapidly achieved through the process.
Additionally, many air cleaners and ambient air ionization units also produce ions of either positive, but more typically, negative polarity.
Air ionization may be performed using electrical ionizers which generate ions in a process known as corona discharge. Electrical ionizers generate air ions through this process by intensifying an electric field around a sharp point until it overcomes the dielectric strength of the surrounding air. Negative corona occurs when electrons are flowing from the electrode into the surrounding air. Positive corona occurs as a result of the flow of electrons from the air molecules into the electrode.
One important factor in ion generation is how rapidly ions can be transferred from the tip of an ionizing pin into an air stream, and ultimately to the desired workspace or target. An emitter assembly is commonly used in ion air blower which emits either or both of positive and negative polarity ions. The emitter assembly is mounted in an air flow path so that air is propelled through an air guide such as an annular ring formed by the interior walls of an ionizer housing. FIGS. 4–5 depict a prior art air ionizer blower 50 having a housing 52 and a conventional finger-guard 51 disposed over an outlet of the air ionizer blower 50. Ionizing pins or other electrodes extend generally radially inwardly from the annular ring so that their tips are positioned in the air flow to allow ions to be blown off or drawn off of the ionizing pins and out of the ion air blower 50 which houses the emitter assembly. It is common to use an air mover, such as a rotary-hub fan or axial fan or tube-axial fan, to drive or draw air through the air ionizer blower 50. One drawback of the conventional finger-guard 51, as demonstrated in FIG. 4, is that the air that is not directed in a particular direction, and therefore, loss-causing air flow patterns such as eddy currents, swirls, vortices, rotational swirls and non-linear trajectories detract from or inhibit the air flow directed toward the work space. Further, some of the air flow that is not even loss-causing, has a trajectory other than toward the work space or target.
The typical air flow output of an axial fan has some velocity in the direction away from the fan (X direction, perpendicular to the face of the fan) and velocity elements in the tangential directions (Y-Z plane, parallel to the face of the unit). The net effect is for the air coming from the fan to have significant swirl. Fan swirl is well understood and modeled by computational fluid dynamics. For an application such as an ionizer (see, for example, prior art air ionizer blower 50 in FIG. 4) where the output of the axial fan is used to target a critical area, the tangential velocity components of the fan swirl are undesirable, as they lack directionality towards the work space or target area. Commercially available fan guards, such as conventional fan finger-guard 51 (FIG. 4) are comprised of elements with rounded or oval cross sections. In the case of wire form finger-guards 51, the rounded metal elements minimize resistance to air flow in any direction. Similarly, plastic finger-guards 51 do little to impact the directionality of the output air flow. In either case, this relatively isotropic resistance to the air allows flow to move away from the fan with little impact on velocity components tangential to the output direction of the ionizer.
Because the air flow does not reach the work space target rapidly or thoroughly, the ions are not transported to the work space or target efficiently. Additionally, in the case of bipolar ionizers, the loss-causing air flow patterns also result in the recombination and/or cancellation of positively and negatively charged ions further detracting from the efficiencies of the system. Moreover, the optimal efficiency of the air mover or fan is also not fully realized because much of the discharged air that is not channeled never even reaches the work space or target.
Accordingly, it is desirable to provide an air ionizer blower configured to redirect the air flow toward the work space or target. Further, it is desirable to configure such an air ionizer blower to attenuate loss-causing air flow patterns to improve the efficiency with respect to air flow and the distance that ions are carried.